Escherichia coli is the most common cause of community-acquired urinary tract infections, resulting in an estimated eight million physician visits a year in the United States. It is also a leading cause of nosocomial infections. Pathogenic E. coli strains carry groupings of genes which are absent in strains that do not cause infection of the urinary tract. These clusters of extra genes have been termed "pathogenicity islands (PAI's)", and the hypothesis to be tested is that they code for the factors necessary in the development of cystitis, pyelonephritis and sepsis. The basis for this hypothesis is the homology of some PAI sequences to virulence genes recognized in other pathogens such as Salmonella, Shigella, Yersinia, Serratia, Vibrio, Bordetella and Streptococcus. Putative virulence genes will be identified on the basis of homologies to sequences of known virulence genes. They also will be found by signature-tagged mutagenesis of a wild-type uropathogenic strain and negative selection of avirulent mutants in a murine model of ascending urinary tract infection. The mouse model will be used to confirm the loss of virulence of signature- tagged mutants as well as test specific allelic knock-outs of candidate virulence genes identified by sequence homologies. New virulence genes will be further examined at the molecular level with analysis of expression conditions and characterization of translation products. The goal of this project is to further the understanding of the mechanisms that underlie the ability of these uropathogenic E. coli to cause disease. The information will promote the development of new chemotherapies and vaccines. The performance of this research plan requires an investigator with a background in basic research. The candidate for this award has worked a year at the NIH and a year so far in the laboratory of the sponsor. The sponsor has more than two decades of research experience in this field and has trained eight Ph.D.'s and six postdoctoral fellows. He heads a fully-equipped and expertly- staffed laboratory at a large university with a distinguished record of research success. The combination of the experience gained in this research, the mentorship given by the sponsor and the educational opportunities offered by the university will accomplish the second goal of this project and meet the ambition of the award candidate: to launch a career as an independent academic investigator.